[Qemu-devel] Re: [PATCH RFC] virtio: add features qdev property

[Gerd Hoffmann]

On 12/14/09 10:42, Michael S. Tsirkin wrote:
> On Mon, Dec 14, 2009 at 10:41:26AM +0100, Gerd Hoffmann wrote:
> > On 12/13/09 21:43, Michael S. Tsirkin wrote:
> > > Add features property to virtio. This makes it
> > > possible to e.g. define machine without indirect
> > > buffer support, which is required for 0.10
> > > compatibility. or without hardware checksum
> > > support, which is required for 0.11 compatibility.
> >
> > I'd suggest to add flags for the individual features to the drivers
> > which actually use it instead, so you'll have
> >
> >    -device virtio-net-pci,hw-checksum=0
> >
> > and
> >
> >    -device virtio-blk-pci,indirect-buffers=0
> >
> > cheers,
> >    Gerd
>
> Hmm. I hoped to avoid it, there are lots of features so it's a lot of
> work and in practice, this will most likely be set by machine
> description ...

MSI-X aka vectors property is already done this way, so I'd tend to 
continue this way.  It is also more user friendly.  Sure, these are most 
likely not used on a daily base by users, but being able to turn off -- 
say -- indirect buffers for testing and/or bug hunting reasons without 
having to construct magic hex numbers from virtio header files would be 
nice.

Can you give a list of features?  The patch description sounded like it 
is just the two listed above ...

cheers,
  Gerd